In certain type of jet engines, Engine Electronic Controls (EEC) units fail at an unusually high rate. Failures of these EECs are caused by the thermal cycling that occurs in a typical flight evolution. Presently, the EEC is cooled on the ground by natural convection when the jet engine is off. When the engine is on while on the ground, at takeoff power or climb, cooling air is drawn through the EEC and into the engine by low pressure produced at the engine inlet. When at altitude, the flow is from the engine inlet into the EEC due to pressure changes. Thus, a typical EEC may experience in a single flight a range of temperatures between minus 60° C. and plus 95° C. Because of the extreme differences in these operating temperatures, thermal expansion and contraction of the electronic components within the EEC occurs, thereby leading to thermal fatigue and failure. When failure occurs, the engine may be shut down. In the air, this is critical and the aircraft must land at the nearest airport. On the ground, the engine must be shut down and engine maintenance must occur. Both of these shutdown situations are very costly to both the airlines and the engine/aircraft manufacturers due to guarantees. In-flight shutdown typically costs thousands of dollars due to an aircraft having to land at a non-destination airport, and a back-up aircraft having to be called or other form of transportation arranged for the passengers. There are also the unmeasurable costs associated with adversely affecting the travel plans of all the occupants of the aircraft.
In situations when an on-ground engine shutdown occurs, departure is delayed trying to resolve the problem. This can be very costly if the EEC has to be replaced. Also, the time it takes to perform the maintenance or find a new aircraft also costs a great amount of money for the airlines as well as adding to unmeasurable cost of passenger delay.
Therefore, there exists a need to reduce the amount of thermal cycling that can occur in various machinery, including, for example, aircraft EEC units.